Phillips Magnavox 51MP392H/17 51" color/video problem

I recently got a phillips 51" 51MP392H/17 for free, the picture comes in, but like other posts, at the bottom of the screen there is a half circle blue, red going up about a third of the way. And when there is text like channel etc. on the screen or other places, sometimes it looks like 3D without the glasses on. Kind of double vision. The person I got it from said someone told her it sounded like it just needed the "green tube" replaced. I don't know about TVs and can't find a service manual (there was one link for a 10mg text doc., but wouldn't open...just garble), but from reading other posts, is there a way (combination of numbers on the remote) to type something in for self repair/diagnosis to correct this problem? I read something about "service mode" but can't figure out how to get it into that. I'd like to take care of this cheap, but don't know anything about TVs. Can someone suggest how to get it in service mode, how to adjust the double vision problem and/or give me a link for a good .pdf service guide for this model? It's only 4 years old. Please help! Thank you very much.